Conventionally, as a rotating electrical machine used and mounted on a vehicle, a field rotating type synchronous motor (hereinafter, referred to as an IPM motor) with a structure that permanent magnets are embedded inside a rotor is known.
Since it is possible to utilize both reluctance torque by magnetization of the rotor and torque by magnetization of the permanent magnets, the IPM motor is highly efficient and thus preferably employed in a hybrid vehicle or an electric vehicle, etc.
Such an IPM motor includes a stator that functions as an armature and a rotor that functions as a field system disposed so as to face the stator in a radial direction.
In Japanese Patent Application Laid-Open Publication No. 2-294241, there is disclosed a rotor that includes a shaft (rotational shaft) having a knurled portion formed on an outer peripheral surface thereof, and a rotor core having a fitting hole that is fitted and fixed to the knurled portion of the shaft by press-fitting.
In addition, in Japanese Patent Application Laid-Open Publication No. 11-69675, there is disclosed a rotor (field winding type rotor) that includes a shaft having a knurled portion formed on an outer peripheral surface thereof and a stepped portion formed on an axial end portion, a rotor core (cylindrical core) fitted and fixed to the knurled portion of the shaft, and a collar that is fitted and fixed by press-fitting to another axial end portion of the shaft.
Incidentally, in the case of the Publication No. 2-294241, foreign matter such as shavings of a press section occurs when the rotor core is fitted and fixed by press-fitting to the knurled portion of the shaft.
Since this foreign matter is scattered by centrifugal force during a rotation of the rotor, this may reduce insulation properties due to damage to stator windings, a cleaning process is required, and it becomes a reason for causing high cost.
Moreover, even in the case of the Publication No. 11-69675, foreign matter such as shavings of a press section occurs when the rotor core is fitted and fixed by press-fitting to the knurled portion of the shaft.
Therefore, when the collar is press-fitted to the other axial end portion of the shaft, the foreign matter would be caught, and a problem of lowering a press-fixing force, or a problem that the collar cannot be pressed into a predetermined position may arise.
In addition, in the case of Publication No. 11-69675, the number of parts increases due to the use of the collar, and there is also a problem of it being higher in cost.